Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$122.59	4.300%	$127.8614	$127.86	$127.85	$127.90
Purchase #2	$72.26	8.328%	$78.2778	$78.28	$78.30	$78.30
Purchase #3	$112.48	11.589%	$125.5153	$125.52	$125.50	$125.50
Purchase #4	$177.69	9.358%	$194.3182	$194.32	$194.30	$194.30
Purchase #5	$95.87	7.757%	$103.3066	$103.31	$103.30	$103.30
Purchase #6	$225.65	13.462%	$256.027	$256.03	$256.05	$256.00
Purchase #7	$85.67	5.441%	$90.3313	$90.33	$90.35	$90.30
7 purchase totals =	$892.21		$975.6376	$975.65	$975.65	$975.60